(1) Field of the Invention:
This invention relates to a printed or coated material or article (hereinafter called "print" for the sake of brevity) making use of an infrared reflective coloring agent and its production method, and more specifically to a print obtained by printing or coating a base material with a printing ink or coating formulation (hereinafter called "printing ink" for the sake of brevity) containing an infrared reflective coloring agent and another printing ink containing an infrared absorptive coloring agent and a method for the production of the print.
(2) Description of the Prior Art:
As a one way to cope with electrophotographic forgery of negotiable securities such as share certificates and public and corporate bonds, airline tickets, checks and the like, it has conventionally been practised to print in advance anti-forgery words and/or pattern in a hidden form on such prints. As a method for facilitating discovery of forged items, it has been proposed, for example, to print beforehand a magnetic mark in the form of letters, symbol, pattern or the like with a magnetic ink and to determine their genuineness or spuriousness by means of a magnetic reader.
The above-mentioned hidden letters or patterns in negotiable securities are themselves effective means for the prevention or discovery of forgery. It is not easy to use such hidden letters or patterns in simple prints because they require a printing technique of high level. In addition, such hidden letters or patterns may not be used widely since a limitation is imposed by their use on permissible designs and patterns.
The method which makes use of magnetic marks is insufficient in reliability, since the intensity of the magnetism is changed or the magnetism is lost entirely when the magnetic marks are exposed to heat or are placed in an environment of high magnetic field or the like.